Manufacture of rubber



Patented Nov. 11, 193

3 U NITED STATES WILLIS A; BOUGII'IOYN, or CAMBRIDGE, MASSACHUSETTS MANUFACTURE OF RUBBER no Drawing,

yThis invention relates to improvements in the manufacture ofrubb'er. ,More especialrly itrelates to the use of chemical processes in, connection with rubber in emulsified form,

5 as in' latex, inxobtaining vulcanizedrubber.

1 The invention provides r for rubber to be takendirectly from latex, in association with sulfur, or with Selenium or tellurium, in i p 'fiThese ends are attained by mixinga liquid containing sulfur'in'solution, or sulfur in loose combination in solution, with a liquid,-

asflatex, containing rubber in mobile col- -lo1dal"d1spers1on' 1n such manner that-upon drying, afterany reaction that occurs, or

upon precipitation, the rubber and sulfur are left insuch intimate and evenly distributed association that the vulcanization can belefiected by merely heating them. aOfiThis .intimate association =may be purely physical, as appears to be the fact in one case, or there may be achemical combina wtionyas appears to be the fact in another -case. It is' an underlying principle that V 5 the sulfur should be provided in a solution which will mix welllwith latex. the sulfur being either free or in such chemical com- J bination that is released by reaction which does not injure the latex or rubber.

:To this end I have'found that an aqueous ammonia solution of sulfur, or of surfur compound, mixes well with ammoniacal la itexr Upon such mixture being made, a chemical reaction occurs, or a physical Q. vulcanized State whichubas been reflected Application filed July 28,

change, or both, producing a liquid which 1923. Serial no esenes.

without heat; and this residue, when heated tothe iusualivulcanization temperature acquires the physical characteristics of vulcanized rubber. i

The solution or compound may however 5 be produced by adding the sulfur in a combined form more directly to latex, as by adding hydrogen sulfide gas or aqueous solution thereto, upon which the gas is absorbed by and reacts with the liquid, with the same ,6 result as above described.

The invention may be practiced in other modifications as by use ofcompounds or solutions of tellurium and of selenium in place of sulfur; and as by use of sodium sulfideu or other water-soluble sulfides or watersoluble alkalies to make a solution of sulfur.

As an illustrative example, the process first above mentioned will be described.

A solution of ammonium hydro-sulfide having been prepared by passing hydrogen sulfide into a solution of ammonia in water, sulfur isintroduced into the solution by adding free sulfurand heating. The colorless solution becomes yellow, reddish, then deep,. red, as more and more sulfur dissolves, making a solution of ammonium' polysulfide. The combination by which the added sulfur is held is undoubtedly a loose one, one evidence of which is that upon spontaneous evaporationof the solution free sulfur is deposited. This solution, containing dissolved ammonia, as also does commercial latex, mixes well with latex; but the mixture becomes darker than either constituent, turning abluish clay-grey color, depending upon the amount of sulfur carried by the polysulfide solution, the change of color being such as signifies a chemical action or physical 96 change or both. It appears that this is, to a degree, a vulcanization of the colloidal gum particles ofrubber while still suspended in the fluid mixture. When the resulting liquid is allowed to evaporate in sheet form a bluegreen transparent film is produced which when heated to the usual vulcanization temperature loses the characteristic offensive odor of soluble sulfide and becomes a tough, elastic film having the brownish colorand 1 of vulcanized theclaims hereofvvith the sense that the substitution of these other members of the sul- V fur family or their compounds for sulfur or compound of sulfur would be substantially an equivalent Within the meaning of the patent law.

=The's-sulfurzin the -miXtu-re prepared for "---vuleanization may n'ot be -free sulturbut may she-combined in some compound, the precise ed gas becomes" absorbed byth'e latex liquid.

/Vhen absorption ceases the reaction appears 7.

to be at an end. The solution 'being'tl1en allowed to dry darkens from itswdarlrslate blue 7 color to a blue-green black film which when yheated loses any offensive odo1":vvhich'it'. -pos- *ses'ses an'dfibecomes strong, tough .and elastic,

ized. pure rubber.

Eh-e above Edescribed: chemicak solution of sulf urcompounds" in I= latex-may be applied like ,iandfwhensthen heated? the rubber be,-

- 'ized' carrying the fiber as a loading material.

It appears indeedthat' the treated latex may be manipulated mechanically in any Way that untreate'd: latex-can be used.

- fFor the application' of theainvention with the "salts of telluriuin and selenium it is .anot

necessary to use" the poisonous hydridesr I ihave found, what .hirs-tsapparntly been =unnature of which it is not necessary to know,

invvhi'chitis' so looselyheld that upon being heated-it -is.released, and the characteristic incidents and effects ofvulcanization occur.

AS this;;whethe r; free or as a componniis a solution;sand as the colloidal rubber in latex is mobile in vvhat maya'for practical purposes g v be called a colloidal' shlutionpib'oth rubber 1 possessed.of the=L ual1t1esi of a Well vulcan mobile in a wayithaiiis' equivalent to fiuidity and for' whichf I somewhat arbitrarily for brevity herein use the term fluid Itimight be considered that both are d'iSsolved -im a :liquid' vehicle, but, vvhatjever the fg pr'e'cise physical or chemical 'form 'may beg thenpractical situation is th'at the one ibe'comes dispersed throughout thelother. If perchance *there isa' tendency of the l'i'qlui ds to separate,

that tendency preferably 1 i'shoul'd be' combatted by stirring or othe methods; The

application :of heatfglor e a ratin'gr the excess 'liqui'd' V'might s'e'riie f tournaintain such a sknown heretofore, that vgroun'd elemental I} seleniuin idi'ssolves readily in" an aqueous so- F 35 l'lution ofammoniumhydrosulfideto:(produce aascherrysred solution'vvhich can be mixed "vulcanization, care should begtaken tosefthat "too: much 1 heat is noty: thus 'i'applied, i lest' the with latex"Withoutcausing the gum to coag-f *nl'ate This: mixture, when. dry, produces a vfi'hn which has the toughness, elasticity and:

the drying sheet 'becomes. cosine-red and the sheet when drled'ls red. -.'PoWdered tel-lurium ""CllSSOl'VQSOIllY slowly in ammonia hydrosuliide sand -pr-odiu'ces' ;a bluish-grey: solution? V-hen llns as'snnxeduvithlatex the color un-- 'goe's no QbVlfOuSfChaIlgE), except a slight nen-i -ng; abut the 'film if-orms mixture,

what-tar I iea'ctiona tne term other ipropertiesof' a vulcanized gum. The armature changes color, becomingxpink, and

vulcanization be p reinature. -Upon thwdrying, the 'colloidal rubberf becomes a solid :i or

sejmi 'solid 'gel with the 'sulzliur or' sulfuri'conl- "pojund distributed all through i intimate contact; and the twkr areuin equally intimate contactwvithi any foreignTmate-rial,

n extremely filling or: loading material' wh'rch may'ihave ;been maintainedzivvellidistribnted:throughout mwhich -When 5 dried and ahea-ted :ismarkedly vulcanized. Bothrin-ythiscaseaandin the casev "or the selenium,.howevenQthe reactions conthe liquid :"Owing itoistheuniform impregnation of suclrmaterial 'by tlle li'quid fem 'of'the sulfur and'rubbera very per-feet: p'ro d i 1 7 not is-iassured; isallowed to stand, so that eventually a color Considering theproeess as a vvh'olefitiiv ill be observe'dthat it -fdeals'yvitlr reagents which i on' the 'one':r.hand'iare R vulcanizingianaterials such as 'su'lfur; 'seleniumixa'ritellurium, iand a i I J 11rvieW oiithe search'thats been *nifade for larger commercial uses hich 'lnth'erto "have been that act as ear iersrer the uieani z i ng i-na- Ite'ii'als end iwhicha may lie; eliminatd by I V simplevolatilinat-ion.jf flhe ammonia s orv -oi theabove showing of the equivaselenium-aria telluriu'ni to" sulfur, inth *1 bber n miutnres and su1'ur*- wis11 be u'seddn been X and ervlng to' a reserve the L prevent -fermentation; Wsfilfitinof a; theother han d are' solutionsiofi gases' in Water such asiammonia and'hydrogen sulfide,

or fibrous material whichimay have been laid} in the. bottom of the. container ;:?or* with any" a sulfide or hydroxide, or both, of any alkali metal might be added in reasonable quantity to natural latex Without precipitating the gum, it is to be considered that for the purvolatilization from solution. The ammonia should be present in latex in sufficient quantity to prevent any marked undesirable change in the physical or chemical properties of the latex that might otherwise be caused by the addition of an alkaline solution in the process. However, as the latex is itself alkaline the ammonia may in some cases be omitted, and the latex be treated in its natural form with hydrogen sulfide or other reagent for thereby the step of formation of ammoniumsulfide is saved.

It is'intended that the patent shall cover, by suitable expression in the appended claims, whatever features of patentable novelty exist in the invention disclosed.

I claim as my invention:

1. In'the art of vulcanization, the steps of passing gaseous hydrogen sulphide, until absorption lessens substantially, directly into a continuous body of uniformly ammoniacal liquid latex; evaporating the resultin mass to convert it to solid state, thereby eecting partial vulcanization; and subjecting the residuum to the action of heat, whereby complete vulcanization is accomplished.

2. In the art of vulcanization, the steps of passing the gaseous hydride of an element of the sulphur group the atomic Weight of which is at least as high as that of sulphur, until substantial saturation is attained, directly into a continuous body of uniformly ammoniacal liquid latex; evaporating the re- I sulting mass to convert it to solid state, thereby effecting partial vulcanization; and subjecting the residuum to the action of heat, whereby complete vulcanization is accomplished. I p

3. In the art of vulcanization, the treatment of latex with the hydride of an element of the sulphur group the atomic weight of which is not less than that of sulphur which consists in passing said hydride, in the form of a gas and in excess of the amount required in a dispersed state and a hydride of an element of the sulphur group having an atomic Weight not less than that of sulphur, the step of interacting being one which can be efiected in an alkaline vehicle.

6. In the art of making vulcanized rubber, the steps of introducing an excess of hydro gen sulphide gas into a continuous body of liquid latex in which ammonium is present, drying the liquid, and heating the residue to produce the vulcanized rubber.

Signed at Readfield, Maine, this 23rd day of July, 1923.

WILLIS A. BOUGHTON.

to react with the ammonia, into a continuous body of ammoniacal liquid latex.

4a In the art of vulcanizing, the step of passing into an ammoniacal suspension of rubber a gas comprising the hydride of an element of the sulphur family the atomic Weight of which is at least as great as that of sulphur, said gas being in excess of the amount required to react with the ammonia.

5. In the art of vulcanizing, a process which includes the step of interacting rubber 

